1. Field of the Invention
The present invention relates to a gas pressure reduction valve improved in pressure-controlling performance.
2. Description of the Related Art
It is known that a gas pressure reduction valve for reducing pressure of compressed natural gas (hereinafter, referred as CNG) in a fuel gas container of an automobile to a predetermined value for high-pressure gas such as CNG.
In JP-A-11-82780 (pages 3 and 4 and FIGS. 1 to 3), a pressure-controlling spring 21 for biasing a diaphragm 16 downward is interposed between a shell 19 and an screw 20 provided in a cover 15 so that the diaphragm 16 is moved up and down in accordance with balance between the biasing force of the pressure-controlling spring 21 and the fuel force of CNG in a compression chamber 14 to thereby keep the fuel pressure of CNG in the decompression chamber 14 to a predetermined low value.
In JP-A-11-304029 (page 2 and FIGS. 1 and 2), a diaphragm 16 is moved up and down in accordance with balance between the biasing force of a pressure-controlling spring 21 and the fuel pressure of CNG in a decompression chamber 14 so that a valve body 2 connected to a central portion of the diaphragm 17 is moved up against a spring 18 to balance the fuel pressure of a diaphragm chamber 16 in a position where the force of the spring 18 balances with the force caused by the fuel pressure of the diaphragm 17. Reduction in outlet pressure (regulated pressure) caused by increase in the flow rate of fuel is suppressed.
In JP-A-2000-248999 (page 3 and FIG. 1), a pressure-controlling spring 21 for biasing a diaphragm 16 downward is interposed between a shell 19 and an screw 20 provided in a cover 15 so that the diaphragm 16 is moved up and down in accordance with balance between the biasing force of the pressure-controlling spring 21 and the fuel pressure of CNG in a decompression chamber 14, that is, a pressure-controlling valve 10 is opened/closed to thereby keep the fuel pressure of CNG in the decompression chamber 14 to a predetermined low value.
In JP-A-11-82780, only one spring is provided though the pressure-controlling spring 21 for biasing the diaphragm 16 downward is interposed between the shell 19 and the screw 20 provided in the cover 15. The pressure gradient in a secondary pressure outlet cannot be kept constant because the spring constant increases.
In JP-A-11-304029, only one spring is provided though reduction in outlet pressure (regulated pressure) caused by increase in the flow rate of fuel is suppressed compared with the background art because the force of the spring balances with the force caused by the fuel pressure of the diaphragm in an equilibrium position. A pressure of an outlet 5 cannot be kept constant because the spring constant increases.
In JP-A-2000-248999, only one spring is provided though fuel pressure in a decompression chamber can be kept to a predetermined value because a force of the spring balances with the force caused by the fuel pressure of the diaphragm in an equilibrium position. A pressure of an outlet 22 cannot be kept constant because the spring constant increases.